Xmas light string controller

Discussion in 'Circuit Help' started by John12345, Dec 6, 2017 at 5:24 PM.

  1. John12345

    John12345

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    Hi. I want to control 5 Xmas light strings using one of the light string controllers. One controller is not powerful enough to run many of them at once so I would like to amplify the variable signal. One controller puts out a variable voltage from 0 to 110 VDC. Each string has a resistance of 105 ohms. I would need a circuit or transistor or Mosfet that would be capable of 110VDC and an amperage of about 5 amps (for 5 strings). I tried to measure the amperage of each string and read about 0.15 amps so I must be doing something wrong here or my meter is bad. I bought a Mouser mosfet p/n FCPF099N65S3 which I thought would work but I can’t figure out how to put together the circuit. Any help would be appreciated.
     
    John12345, Dec 6, 2017 at 5:24 PM
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  2. John12345

    kellys_eye

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    You might find the controller operates using thyristors and chops the AC waveform rather than producing a DC output.

    Any chance you can show us the insides of the controller?
     
    kellys_eye, Dec 6, 2017 at 5:51 PM
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  3. John12345

    John12345

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    I'm pretty sure it is a dc output since the 120VAC runs thru a rectifier. Pictures are coming.
     
    John12345, Dec 6, 2017 at 6:38 PM
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  4. John12345

    John12345

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    Here are some pictures Control1.JPG Control2.JPG Control3.JPG
     
    John12345, Dec 6, 2017 at 6:49 PM
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  5. John12345

    kellys_eye

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    The rectifiers provide the DC for the COB device (Chip On Board) - that's the black blob on the stand-up PCB.

    IIRC the AC feeds the rectifiers then the unsmoothed (fullwave rectified DC) is fed across the board and to the three thyristors - check the device markings as I'm almost 100% sure they ARE thyristors which are phase switched by the controlling IC.

    You could fit higher powered thyristors quite easily - the diodes should be good for 1A (or 120W) but can also be uprated if required.

    Things is the board is 'live' and so are the wires to the lights! so you need to take particular care no matter what you do.
     
    kellys_eye, Dec 6, 2017 at 7:21 PM
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  6. John12345

    John12345

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    Thanks. I'm looking into it. The thyristors are XL 1225s. You've been a big help.
     
    John12345, Dec 6, 2017 at 9:08 PM
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